Mitochondrial sirtuins,metabolism,and aging

Maintaining metabolic homeostasis is essential for cellular and organismal health throughout life.Multiple signaling pathways that regulate metabolism also play critical roles in aging,such as PI3K/AKT,mTOR,AMPK,and sirtuins(SIRTs).Among them,sirtuins are known as a protein family with versatile functions,such as metabolic control,epigenetic modification and lifespan extension.Therefore,by understanding how sirtuins regulate metabolic processes,we can start to understand how they slow down or accelerate biological aging from the perspectives of metabolic regulation.Here,we review the biology of SIRT3,SIRT4,and SIRT5,known as the mitochondrial sirtuins due to their localization in the mitochondrial matrix.First,we will discuss canonical pathways that regulate metabolism more broadly and how these are integrated with aging regulation.Then,we will summarize the current knowledge about functional differences between SIRT3,SIRT4,and SIRT5 in metabolic control and integration in signaling networks.Finally,we will discuss how mitochondrial sirtuins regulate processes associated with aging and aging-related diseases.

Exosomes from antler stem cells alleviate mesenchymal stem cell senescence and osteoarthritis

Dear Editor,Stem cell therapy holds enormous and revolutionary promise to treat various age-related diseases,such as diabetes,heart failure,and Parkinson’s disease.However,low retention and survival rate of delivered stem cells,partially due to immunological rejection,constitute major hurdles for the clinical implementation of stem cell therapy(Lei et al.,2021a).Since mounting evidence showed that several types of stem cells mainly exert their therapeutic effects through the secretion of paracrine effects,exosomes,which are released by stem cells and execute most paracrine functions,have begun to draw attention in the field(Tran and Damaser,2015).Exosomes are membrane-enclosed vesicles with an average diameter of∼100 nanometers secreted by the cells,containing cytokines.

Hyperthermia differentially affects specific human stem cells and their differentiated derivatives

Dear Editor,The human body operates optimally at a core temperature of 37 degrees Celsius.Homeostasis at this temperature is essential for cellular and physiological functions(Cheshire,2016).However,infectious diseases,inflammation,injury,neoplasia,and elevated climate temperature can cause a regulated rise in body core temperature,i.e.,fever(Pasi-khova et al,2017).Indeed,an acute or chronic increase in temperature leads to detrimental effects on vasculature by altering a number of indices of vascular structure and function(DuBose et al.,1998).

Single-cell transcriptomic atlas of mouse cochlear aging

Progressive functional deterioration in the cochlea is associated with age-related hearing loss(ARHL).However,the cellular and molecular basis underlying cochlear aging remains largely unknown.Here,we established a dynamic single-cell transcriptomic landscape of mouse cochlear aging,in which we characterized aging-associated transcriptomic changes in 27 different cochlear cell types across five different time points.Overall,our analysis pinpoints loss of proteostasis and elevated apoptosis as the hallmark features of cochlear aging,highlights unexpected age-related transcriptional fluctuations in intermediate ceils localized in the stria vascularis(SV)and demonstrates that upregulation of endoplasmic reticulum(ER)chaperon protein HSP90AA1 mitigates ER stress-induced damages associated with aging.Our work suggests that targeting unfolded protein response pathways may help alleviate aging-related sVatrophyand hencedelay theprogressionofARHL.

Large-scale chemical screen identifies Gallic acid as a geroprotector for human stem cells

Dear Editor,The interventions that slow aging or promote healthy aging may provide preventative measures for age-related diseases(Zhang et al.,2015).Therefore,it is crucial to identify drugs that target aging-related pathologies and improve health-span in geroscience research.Using model organisms such as C.elegans and rodents,several small molecules capable of alleviating the onset or progression of aging,including rapamycin,nicotinamide mononucleotide,and metformin,have been discovered(Partridge et al.,2020).However,the safety and efficacy of these chemicals still need in-depth evaluation before clinical applications(Partridge et al.,2020).As a result,it is necessary to identify additional compounds with geroprotective effects for human cells to counteract the general trend of populational aging.However,transforming a promising compound into an approved drug requires enormous resources.Alternatively,repurposing previously approved drugs for new clinical applications offers a more efficient and less costly path toward drug develop-ment.Therefore,testing U.S.Food and Drug Administration(FDA)-approved drugs for geroprotective effects may dis-covernew therapeutics that have already been stringently tested in humans for safety.

Low-dose chloroquine treatment extends the lifespan of aged rats

Dear Editor,Chloroquine(CQ)has long been used as an anti-malarial agent(Wellems and Plowe,2001).Recently,CQ has also been applied to treat viral infection and related diseases(Wellems and Plowe,2001;Huang et al.,2020).However,the safety and efficacy of its applications are still under extensive debate(Solomon and Lee,2009).Here,we discovered that low-dose CQ has a geroprotective effect on physiologically aged rats.Low-dose CQ prolonged lifespan,repressed systemic inflammation,and inhibited fibrosis across multiple tissue types in aged rats.Furthermore,we constructed transcriptomic maps for 6 tissues(kidney,small intestine,liver,heart,lung,and aorta)upon CQ treatment,thus revealing the effects of CQ at a systemic level.CQ treatment mitigated age-related molecular changes and repressed genes linked to fibrosis and the inflammatory response.Altogether,our data provide a valuable resource for investigating the impact of CQ on multiple aged tissues,which may facilitate the development of clinical applications that mitigate age-related changes in the elderly.